Leveling vessel with heat exchange therein



1954 w. M. SIMPSON LEVELING VESSEL WITH HEAT EXCHANGE THEREIN Filed Sept. 27, 1949 Patented Aug. 10, 1954 LEYELINGNESSELWITH HEAT EXCHANGE THEREIN Walter M'FSimpson, Evansville lnd assignor to "servel lnc New York, N. Y., a corporation of Delaware Application September 27, 1949, Serial No. 118,035

1.01aim. 1

The present invention relates torefrigeration and more particularly to the absorption liquid circuit of an absorption refrigeration system.

The presentinvention may be usedin other absorption refrigeration systems butis particularly adapted fOrvacuum type two-pressure absorption refrigeration systemsof the kind illustrated and described in-my prior UnitedStates Letters Patent No. 2,456,455 issued December 14, 1948 entitled Heat Exchanger. Thepatent discloses an absorption-solution. circuit comprising a generator, an absorber and conduitmeans'to provide separate paths of fiow for-solution weak in refrigerant flowing: toward the-absorber and solution strong in-refrigerant flowing toward the generator. .A'vapor liquid li'ft utilizing .refrigerant vapor expelled in the generator raises the solution-for gravity flowthrough the --circuit. Aheat exchanger in the circuit transfers heat from the. relatively-hot. solution flow ing from the generator totherelat'ivelycold solution flowing toward the generator and a separate reservoir vessel located above the base of the generator receivessolutionfrom the heat .exchangerand maintains a hydrostatic reaction head-on the vapor liquid-Mt.

One of the objects of the'present invention is to provide a unitary-structure.in'the-solution circuit for exchangingheat-betweenthe solution in the separate paths of} flow-and maintain- ,ing a hydrostatic reaction. head onv thevapor liquid-lift.

I Another object. is toprovide .aunitary structure in the. absorption solution circuit which-constitutes a heat: exchanger in its lower portion and a reservoir for solution-in its upper :portion.

Still another object of thepresent invention is to-providea combined :h'eatv exchanger and res-- ervoir vessel which requires less space, fewer parts and less material than theconstructions previously used and which reducesthe heat loss from the heat exchanger.

These and other objects; will become moreapparent from the following descriptionand drawing in which like reference characters denote like partsythroughout the several-views. I-tisto be expressly understood, however, that the drawing is for the purpose of illustration only and :not a definition of the limits of theinv'e'ntion, reference being had forthis purpose to the appended claim. In the drawing:

:Fig. 1 is a diagrammatic. view of :an absorption refrigeration system incorporating-thecombined- .heat exchanger and; reservoir vessel -of the present v invention.

Fig. 2 is an enlarged front sectional view of the combined heat exchanger and reservoir vessel showing one of the compartments of the heat exchanger'and the connections thereto, and

Fig. 3 is a side elevational view of the combined heat exchanger and reservoir vessel partly in section and showing the spaced compartments providing separate paths of flow through and between the compartments.

In the drawing the present invention is shown applied to a vacuum type absorption refrigeration system utilizing water as a refrigerant and a salt solution as an absorbent and is generally similar to that illustrated and described in my prior United States LettersPatent No. 2,456,455 referred to above. The refrigeration system comprises a generator 5, a condensert, an evaporator l, an absorber 8 and heat exchanger 9, later to be described in detail, interconnected to provide circuits for refrigerant and absorbent.

The generator 5 constitutes a vapor liquid-lift and comprises a plurality of upright tubes ll] connected at their lower ends to an inlet chamber H and at their upper ends to a separating chamber l2. Tubes II! are enclosed in a jacket I3 to provide a heating chamber I 4 therebetween. Steam or other heating medium is supplied to the heating chamber Hi from any suitable source through a conduit [5. A vent pipe I6 connects the chamber M to the atmosphere at a point remote from the inlet conduit IE to maintain thesteam in the heating chamber at atmospheric pressure. A condensate'drain I! is provided adjacent the lower v end of the heating chamber Hi. When steam is supplied to the heating chamber [4 its heat is transferred through the tubes I0 and expels refrigerant vapor, such as water, from the absorption solution, such as ,a water solution of a hygroscopic salt, and the expelled vapor acts to lift the solutionin the tubes by a climbing film vapor-lift action to the separating chamber [2.

The separating chamber 2 of the generator 5 may have any desired shape and in the illustrated embodiment is rectangular in side e1eva tion and oval in plan to adapt it to fit the available space. Baiiles l8 and I 9 extend between the sides, of the separating chamber l2 to separate solution from refrigerant vapor and also to strengthen the chamber. The top of the separating chamber I2 is, connected to the condenser 6 by a conduit 20 and the condenser, in turn, isconnected to the evaporator l by a conduit including a liquid receiving vessel 2| and a pipe 22. The vessel 2| in the conduit has an orifice (not shown) of a size to pass all of the liquid refrigerant condensed in the condenser 6 and permit a limited flow of refrigerant vapor to purge non-condensable gases from the condenser as claimed in a co-pending application for United States Letters Patent ofNortonE. Berry, Serial No. 725,000, filed January 29, 1957, now Patent No. 2,563,575, dated August '7, 1951, and entitled Refrigeration.

Evaporator '5' comprises a plurality of substan-.

tially horizontal finned tubes 23 extending between headers 24. The pipe 22 from the condenser 6 extends into one end of the uppermost tube 23 for delivering refrigerant thereto. Cups 25 in the headers 24 receive refrigerant flowing from the end of each tube and direct it into the next lowermost tube so that refrigerant flows successively through the tubes from the top to the bottom of the evaporator. municate with the interior of the absorber 8 to permit refrigerant vapor evaporated in the evaporator 1 to flow to the absorber. Mounted in the absorber 8 is a bank of cooling coils 25 to which cooling water is supplied through the header 2? and supply pipe 23 from any suitable source such as a city water main, cooling tower or the like. Cooling water from the bank of cooling coils 26 is delivered through a header Z9 and conduit to the inlet of the condenser E and is exhausted from the condenser through a conduit 3 i.

The absorption solution circuit comprises a path of flow for solution weak in refrigerant fiowing from the separating chamber l2 of the generator 5 to the top of the absorber 8 and a path of fiow for solution strong in refrigerant flowing from the bottom of the absorber to the inlet chamber l I at the bottom of the generator. The path of flow for solution weak in refrigerant or,

in other words, concentrated salt solution includes the conduit 32, inner passages of heat exchanger 9, conduit 33 and liquid distributor 34. The absorption solution is divided by the liquid distributor 34 for flow over the cooling coils 26 in the absorber 8. tion solution strong in refrigerant or, in other words, dilute salt solution includes conduit 35, outer passages of the liquid heat exchanger 9 and conduit 36 to the inlet chamber ll of the generator 5. of the generator 5 flows by gravity from the separating chamber [2 at the top of generator 5 to the liquid distributor 34 in the absorber 8 and from the bottom of the absorber to the inlet chamber 1 I at the bottom of the generator.

The generator 5 and condenser 6 operate at pressure corresponding to the vapor pressure of the refrigerant at its condensing temperature and the evaporator and absorber 8 operate at a lower pressure corresponding to the vapor pressure of refrigerant in the absorbent at the temperature of the absorbent. The difference in pressures in the condenser 6 and evaporator I is maintained by the orifice in the vessel 2| and the difference in pressures in the absorber 8 and generator 5 is maintained by liquid columns in the conduits 33 and 35. The liquid level in the con duit 35 is indicated by the reference character X while the liquid level in conduit 32 connected to the conduit 33 through the heat exchanger 9 is indicated by the reference character Y.

A purge device 37-, is provided for continuously withdrawing non-condensable gases from the ab sorber 8 and transferring them to an inactive part of th system. Sufiice it to state herein that The headers 24 com- The path of flow for absorp- The solution lifted in the tubes H1 4 the purging device 3? is in the form of an auxiliary absorber connected to withdraw non-condensable gases from the absorber 8 and deliver the gases between alternate slugs of absorption solution through a fall tube pump 38 to the lower end of a riser tube 39. The non-condensable gases ascend through the riser'tube 39 to a storage vessel 40 and the absorption solution flows through the connection 4| to the return conduit 35. The non-condensable gases may be removed from the storage vessel from time to time by an exhaust pump 42.

A concentration control vessel 53 is connected to the lowermost cup 25 in the evaporator l by a conduit 44 and to a header 24 by a conduit 45. The bottom of the concentration control vessel 43 is connected to the inlet chamber ll of the generator 5 by a conduit 46. During operation of the refrigeration system a quantity of liquid refrigerant, water, will be stored out of solution in a liquid column in conduit 45 and concentration vessel 43 and the height of the liquid column or quantity of liquid stored in the concentration vessel will vary with variations in the difference in pressure between the evaporator I and generator 5. As thus far described the refrigeration system is substantially identical with that illustrated and described in my prior Patent No. 2,456,455 except for the purge pump and concentration vessel and their connections.

In accordance with the present invention the heat exchanger 9 is so constructed and. arranged as to constitute a reservoir for absorption solution to maintain a hydrostatic reaction head of substantially constant height on the generator 5 while permitting variation in the amount of solution stored therein.

The combined heat exchanger and reservoir vessel 9 comprises a plurality of closed compartments 55 arranged in spaced side by side relationship in a casing 5! to provide alternate passagesthrough and between said compartments for solution weak in refrigerant and solution strong in refrigerant, respectively. The lower portion of casing 5i encloses the compartments 5i) and its upper portion extending above the compartments to provide a reservoir chamber 52 for storing absorption solution. A vent tube 53 connects the top of reservoir chamber 52 to the separating chamber l2 to equalize the pressure on solution in the chamber with the pressure on the solution in the generator tubes 5. The compartments are of the same construction as illustrated and described in detail in my prior Patent No. 2,456,455, referred to above. Suffice it to state herein that each compartment 50 comprises a pair of reversed plates 54 having ofi'set peripheral flanges 55 welded together to provide an enclosed space therebetween. Each plate 54 has bosses '55 projecting from opposite sides thereof for abutting engagement with similar bosses on adjacent plates to hold the plates of each compartment in space relationshi and the plurality of compartments spaced from each other. The compartments 50 have openings 51 at the top connected by a header 58 and openings 59 at the bottom connected by a header 65. While the compartments 55 may have other shapes they are preferably of octagonal outline with their lower portions conforming to the bottom of the casing 5! on which the flanges 55 seat. With such a construction the entire area of the plates 54 and headers 58 and 50 constitute heat transfer surfaces without any pockets of stagnant liquid in the direction of flow. Con- .du-it 32 connects the .bottomof the separating chamber 12 to the upper headerr58 andconduit .33 connectsthe lower header 6!) .tov the liquid distributor at the :top of the absorber 8. Thus, the passages through the compartments: 50 constitute. a path of. flow' for solution weak in refrigerant flowing from the generator 5'to the absorber 8. -.Conduit.; connects thev bottom of the absorber 8 to the bottom of the casing 51 and conduit 3.6 connects the side of. the casing above the compartments 5!] to the inlet chamber H of the generator 5. Thus, the passages between the compartments .5!) and between the compartments and the sideof the casing 5| constitute a path of flow for solution strong in refrigerant flowing from the absorber 8 to the generator 5.

The chamber '52 above the compartments 50 in heat exchanger 9 constitutes a reservoir for solution strong in refrigerant which will stand at some level Z in chamber 52 to maintain a hydrostatic head of a predetermined height on the inlet chamber ll of generator 5. Due to the relatively large cross-sectional area of chamber 52, changes in the amount of solution in the chamber will produce only very slight changes in the height of the liquid level so as to maintain the hydrostatic reaction head substantially constant. Also, the warmer solution from the generator '5 flows through the inner passages while the relatively cooler solution from the absorber flows through the outer passages and between the compartments 50 and sides of the casing 5| to reduce the heat loss from the heat exchanger 9. One form of the invention having now been described in detail, the mode of operation is explained as follows.

Between periods of operation the absorption solution will have drained into the combined heat exchanger and reservoir vessel 9 and will stand at the same level above the level Z in reservoir chamber 52 and generator tubes l0. To initiate a cycle of operation steam or other heating medium is supplied through the conduit IT to the chamber l4 of generator 5 and its heat is transferred through the walls of the tubes H] to expel refrigerant vapor from absorption solution. The vapor at low pressure will rise through the tubes with considerable velocity and lift absorption solution from which the vapor has been expelled into the separating chamber 12. Refrigerant vapor then flows from the separating chamber I2 through the conduit 20 to condenser 6 wherein it is liquefied and the liquid refrigerant fiows by gravity through the conduit including the vessel 2! and pipe 22 into the top of the evaporator 1.

The absorption solution weak in refrigerant flows by gravity from the separating chamber l2 to the liquid distributor 34 in the absorber 8 in the path of flow including the conduit 32, compartments 50 of the heat exchanger 9 and conduit 33. The solution is divided by liquid distributor 34 for gravity flow over the coils 26 in the absorber 8 in thin films to produce a comparatively large surface area for absorption of refrigerant vapor flowing from the evaporator tubes 23 through the headers 24. The absorption of refrigerant vapor in the absorber 8 reduces the pressure in the evaporator 1 to the vapor pressure of the refrigerant in the absorbent at the temperature of the cooling water which causes evaporation of refrigerant in the evap-' orator at that pressure to produce a refrigerating effect on a medium, such as air, passing over the exterior of the evaporator tubes 23. 1

Solution will be withdrawn continuously from the reservoir chamber 52 and delivered to the absorber 8 until such time as the solution flows back from the absorber 8 to the casing 5| of the heat exchanger 9 at the same rate as it is delivered to the liquid distributor. At such time a condition of equilibrium will have been reached when the solution stands at some level such as Z to maintain a hydrostatic reaction head of a predetermined height on the solution in the tubes I 6. During operation of the refrigeration system conditionsmay change so that more or less solution is stored in the reservoir chamber 5| but due to its relatively large cross-sectional area such changes will have little effect on the height of hydrostatic reaction head. With a substantially constant reaction head and heat transfer in generator 5, a substantially constant amount of solution will be delivered from the generatorj'5 to the absorber 8. The solution'fiowing from the absorber 8 enters the casing 5| of combined heat exchanger and reservoir vessel 9 at the bottom thereof and flows upwardly in the passages between the space compartments 50 and between the end compartments and side walls of the easing to replace the liquid being withdrawn through conduit 36. Thus, the only heat loss in the heat exchanger 9 is from the relatively cold solution.

During operation of the system a measured small quantity of absorption solution weak in refrigerant flows through the auxiliary absorber 31 to withdraw non-condensable gases from the absorber 8 and deliver them through the fall tube pum 38 to the lower end of the riser tube 39. The non-condensable gases ascend in the riser tube 33 and enter storage vessel 40 and the solution flows through the conduits 4| and 35 to the casing 5| of the heat exchanger.

Any unevaporated liquid refrigerant will flow from the lowermost tube 23 of the evaporator 1 into the concentration vessel 43 and be stored therein to increase the concentration of the remaining absorption solution. Such storage of liquid refrigerant in the concentration vessel 43 will reduce the amount of liquid circulating in the system but due to the relatively large crosssectional area of the reservoir 52 such storage of liquid will have little effect on the hydrostatic reaction head on the generator 5. The refrigeration system Will continue to operate in the manner explained above until the supply of heat to the generator 5 is shut off, at which time the solution and refrigerant will drain to the lowermost part of the system and accumulate in the reservoir chamber 52.

It will now be observed that the present invention provides a combined heat exchanger and reservoir vessel in a unitary structure for transferring heat between solution in different paths of flow and maintaining a substantially constant hydrostatic reaction head on the vapor liquid lift. It will also be observed that the present invention provides a combined heat exchanger and reservoir vessel in the absorption solution circuit having heat exchange means in the lower portion of the vessel and a reservoir chamber above the heat exchange means. It will still further be observed that the present invention provides a combined heat exchanger and reservoir vessel which reduces the space requirements, requires fewer parts and less material and reduces the heat loss from the system.

While a single embodiment of the invention is herein illustrated and described, it will be understood that modifications may be made in the construction and arrangement of elements without departing from the spirit or scope of the invention. Therefore, without limitation in this respect the invention is defined by the following claim.

I claim:

In an absorption refrigeration system, a circuit for absorption solution comprising a generator, an absorber, conduit means connecting the generator and absorber to provide a path of flow from the generator to the absorber for absorption solution weak in refrigerant and a path of flow from the absorber to the generator for absorption solution strong in refrigerant, said generator having at least one upright tube in which solution is lifted by vapor expelled therefrom, and a combined heat exchanger and reser-- voir vessel adjacent the generator and comprising a casing forming a unitary chamber connected in the path for solution strong in refrigerant,

heat exchange structure in the lower part of the chamber and connected in the path for solution weak in refrigerant, said chamber being of a height to provide a storage space above the heat exchange structure for storing solution and maintaining a hydrostatic reaction head on the vapor liquid-lift tube, and said chamber having a crosssectional area to maintain a substantially constant liquid level with varying operating conditions during operation of the system.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,091,757 Hanny Aug. 31, 1937 2,122,361 Ullstrand June 28, 1938 2,247,107 Waterfill June 24, 1941 2,287,281 Thomas June 23, 1942 2,399,922 Grossman May 7, 1946 2,456,455 Simpson Dec. 14, 1948 2,513,124 Weiks June 27, 1950 

